A TimThumb error has occured

The following error(s) occured:

The remote file is not a valid image. Mimetype = 'text/html' File = /var/www/html/timthumb/cache/timthumbg30kr6

Query String : w=640&zc=1&src=http://www.campingmolinoafuoco.com/gestione/uploads/photo/25893_10346592_960529733978951_4007727644062896801_n.jpg
TimThumb version : 2.8.13